Polyolefin-based resins such as polypropylene and polyethylene are thermoplastic general-purpose resins, low in price, and have many excellent properties such as moldability, chemical resistance, weatherability, water resistance, and electric characteristics. Given these circumstances, they have been conventionally used in wide fields as sheets, films, molded articles, and the like. However, base materials made of these polyolefin-based resins (hereinafter, also referred to as a “polyolefin-based base material”) are low in polarity and crystalline and are thus poorly adherable base materials and have a drawback in that the adhesion and application of polyolefin-based resins and the adhesion and application of high-polarity substances are difficult unlike polar base materials such as polyurethane-based resins, polyamide resins, acrylic-based resins, polyester resins, and metals.
As to a method for improving the adhesion of the polyolefin-based base material, surface treatment has been conventionally performed on the base material. Examples of the surface treatment include roughening by polishing and introduction of polar groups by oxidants, corona discharge, plasma treatment, and flaming treatment; these means have drawbacks in that they are low in the reproducibility of an adhesion improvement effect and the effect reduces with the passage of time and are not widespread among the general public.
Given these circumstances, a method is devised that applies a pretreatment agent having adhesion to a base material to the surface of the base material in advance. Such a pretreatment agent is called variously depending on its use; it is called an adhesive, a binder, or a primer, for example. Resins having certain properties are used for the pretreatment agent, for example; provided are hot-melt pretreatment agents that involves melting by heat to make a binder or the like, solvent-based ones in which a resin is dissolved in a solvent, aqueous ones in which a resin is emulsified with a surfactant or the like, and the like.
A binder resin solution composition is disclosed that contains a modified polyolefin resin modified with derivatives of an unsaturated polycarboxylic acid and methacrylic acid and a mixed solvent of an alicyclic hydrocarbon and an aromatic hydrocarbon, for example (Patent Literature 1).
A resin composition for plastic paint is disclosed that contains an acrylic copolymer obtained by copolymerizing a certain monomer such as a methacrylic acid alkyl ester in the presence of a chlorinated polyolefin-based resin and an epoxy resin (Patent Literature 2). A binder resin composition is disclosed that is obtained by graft polymerizing (meth)acrylic acid or the like to a chlorinated polyolefin-based resin (Patent Literature 3).
A binder resin is disclosed that is obtained by graft copolymerizing 2-hydroxyethyl acrylate to a resin obtained by reacting a chlorinated polyolefin-based resin, an organic diisocyanate, and a polymer polyol (Patent Literature 4). An adhesive composition is disclosed that contains a resin obtained by reacting a polyurethane component obtained by reacting a certain polyester polyol and an organic isocyanate compound with a (meth)acrylate monomer or the like in the presence of a chlorinated polyolefin-based component (Patent Literature 5).